Tech trends: metadata
- Article 2 of 3
- GIS Europe, December 1998
Files. If your hard drive is anything like mine, it's full of them. At last count, I had nearly 11,000. Do I know what they all do? No. If I needed to find a particular one in a hurry, would I be able to? No. Is there a risk of my using the wrong file or duplicating my efforts? Yes.
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Usually, none of this is quite seamless to the user, who has to change his or her work styles to take into account whether the file is stored loosely or in a database and therefore how to create the accompanying metadata. What's needed for a unified method of data access and metadata creation is to remove the necessity for separate interfaces for access to files and databases.
One way is to store all your files in your database system and this is what the major gis companies are encouraging us all to do now. In the long term, that's what we all will be doing. In the interim, though, most of us still have an incredible number of files sitting loose on servers and hard drives that we simply don't have the time to convert and load into spatially enabled databases.
If you're an esri user, a stopgap method is to install sde for Coverages on your file server and sde for relational database systems on your database server. You'll only have to use one method to obtain your data since both versions of sde have exactly the same interface for access.
Database giant Oracle has IF, the Internet Filing System. This stores all files, whether they're gis or word processing files, in a database which you can access over the Web or through the desktop. In the latter case, the database will appear to be a mounted file server that you can browse as you would any other filing system. You can even use the standard open and save dialog boxes to access the files. Ifs will combine this filing technique with a detailed metadata system you can access from a separate program to locate your files.
IFS's drawback is that the database system has to understand the type of file it's given to store. Initially, this won't include gis files, but when ifs's software development kit comes out in Spring, I suspect gis vendors will be creating plug-ins as quickly as possible so that Oracle Spatial (aka Oracle Spatial Data Cartridge) can store their data formats.
Intergraph's GeoMedia goes in the other direction and doesn't distinguish between files and databases, regarding each as “data servers”. You log on to a data server, be it Oracle Spatial, an Access database, or a MapInfo mif/mid file for example, and GeoMedia will regard each as a database you can query, extract geometry from and so on. Neither GeoMedia nor GeoMedia Professional has its own proprietary file format, Intergraph recommending you save your data into either Access or Oracle Spatial. At the moment, there's no metadata system either, but since GeoMedia is customisable using any standard development package, you can create your own metadata installer without much difficulty (although that's easier said than done).
Does this mean that files are going to die out in the corporate world and the database become the new storage format? The answer is probably not. In the short-term at least, according to Xavier Lopez, senior product manager at Oracle's spatial products/data server division, ifs will sit alongside ordinary files and won't supplant them. You'll also always need to exchange files with other organisations and a database is too bulky for that purpose, never mind the security implications of opening your corporate database to the outside world. Nevertheless, a real move towards the benefits offered by object-oriented relational database systems and metadata is going on within the gis world and it won't be long before the unidentifiable, untraceable file will become almost a thing of the past.
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